The present invention relates generally to circuit breaker systems. More particularly, the present invention relates to a circuit breaker system equipped to provide overcurrent protection and application specific module (ASM) instantaneous overcurrent indication.
Circuit breakers are used to protect electrical circuitry from damage due to an overcurrent condition, such as an overload, a relatively high level short circuit, or a ground fault condition. To perform this function, circuit breakers presently include a switch unit and a trip unit. The switch unit is coupled to the electrical circuitry (i.e., lines and loads) such that it can open or close the electrical path of this electrical circuitry. The switch unit includes a pair of separable contacts per phase, a pivoting contact arm per phase, an operating mechanism, and an operating handle.
For each phase, a first contact of the pair of separable contacts is supported and moveable by the pivoting contact arm and a second contact is substantially stationary. All of the pivoting contact arms are coupled to the operating mechanism, and the operating mechanism is coupled to the operating handle. The operating handle is substantially disposed on the outside of the switch unit. In this manner, the operating mechanism can simultaneously actuate the pivoting contact arms, thereby either engaging or disengaging the pairs of separable contacts, in response to manual manipulation of the operating handle (i.e., a switch). Thus, in the overcurrent condition, all the pairs of separable contacts are disengaged or tripped (i.e., opening the electrical circuitry), and when the overcurrent condition is no longer present, the circuit breaker can be reset such that all the pairs of separable contacts are engaged (i.e., closing the electrical circuitry).
In addition to manual overcurrent protection via the operating handle, automatic overcurrent protection is also provided via the trip unit. The trip unit, coupled to the switch unit, senses the electrical circuitry for the overcurrent condition and automatically trips the circuit breaker. When the overcurrent condition is sensed, a tripping mechanism included in the trip unit actuates the operating mechanism, thereby disengaging the first contact from the second contact for each phase. Typically, the operating handle is coupled to the operating mechanism such that when the tripping mechanism actuates the operating mechanism to separate the contacts, the operating handle also moves to a tripped position.
There are two types of trip units: a thermal-magnetic trip unit and an electronic trip unit. The thermal-magnetic trip unit is a mechanical system that utilizes thermal or magnetic field changes in one or more components within the trip unit to sense the overcurrent condition. The electronic trip unit is an electronic system that includes, among others, circuitry, current transformers, and solid-state devices to sense the overcurrent condition. Because electronic trip units, referred to as ETUs, include solid state devices, they are capable of providing much more than just sensing the overcurrent condition.
For example, the circuit breaker employing the electronic trip unit can monitor and specify, among others, the various types of overcurrent trip conditions, such as a long time trip, a short time trip, an instantaneous trip, or a ground fault trip, and the load conditions at the time of trip, such as the overcurrent value and the overcurrent duration. Such information or data can be provided to an operator via a display, such as a liquid crystal display (LCD) included in the electronic trip unit, referred to as an LCD trip unit or an LCD ETU. Presently, however, the data processed by the electronic trip unit is prone to unreliability and/or degradation due to limitations in the data processing scheme and/or powering of the electronic trip unit.
Thus, there is a need for a circuit breaker capable of providing reliable overcurrent trip indication data. Further, there is a need for a circuit breaker system capable of acquiring, processing, and managing a variety of overcurrent trip indication data corresponding to a series of overcurrent conditions.
One embodiment of the invention relates to a system for sensing and indicating an overcurrent condition in an electrical circuitry. The system includes a trip unit configured to sense the overcurrent condition. The system further includes a module coupled to the trip unit and configured to selectively control power to the trip unit in response to an indication signal transmitted from the trip unit. By selectively controlling the power to the trip unit, this permits communication of a data corresponding to the overcurrent condition and permits configuring the trip unit to sense a subsequent overcurrent condition.
Another embodiment of the invention relates to a method of providing an overcurrent protection and indication for an electrical circuitry. The method includes (a) sensing an overcurrent condition with a trip unit, and (b) initiating a trip to protect the electrical circuitry in response to the overcurrent condition. The method further includes (c) transmitting an indication signal to a module coupled to the trip unit, and (d) controlling a power to the trip unit by the module. The method still further includes (e) communicating a data corresponding to the overcurrent condition to the module.
Still another embodiment of the invention relates to a system for sensing and indicating an overcurrent condition in an electrical circuitry. The system includes means for sensing the overcurrent condition in the electrical circuitry. The system also includes means for communicating an indication signal and a data corresponding to the overcurrent condition. The means for sensing coupled is to the means for communicating. The system still further includes means for selectively controlling a power to the means for sensing and the means for communicating. The means for communicating is coupled to the means for selectively controlling.